In conventional gas turbines a combustor is made from a number of individual burners which feed hot gas into a first stage with nozzle guide vanes that are located downstream of the combustor. The guide vanes direct the hot gases from the individual burners and the air from the compressor stage in a predetermined direction.
In a conventional combustor stage of the turbine, a number of individual burner cans are located circumferentially around the centre of the turbine. Thus, there is some circumferential gas temperature variation associated with the flow of the hot gases from the individual combustor cans in the downstream direction. The periodic circumferential gas temperature variation occurs because between the burner cans a lower temperature at the respective guide vanes is generated and in the vicinity of the circumferential location of the burner a higher temperature at the respective guide vanes is generated.
This circumferential temperature variation leads to a varying temperature profile at each downstream guide vane sector, wherein the temperature profile on each guide vane is dependent on the position of the guide vane relative to the individual burner can, i.e. relative to the installation location of the guide vane inside the turbine.
The vane temperature is a critical aspect to the lifetime of a respective guide vane. Hence, the guide vanes are designed with a predefined heat resistance. The temperature resistance may be increased by the use of cooling air. However, a use of an excessive amount of cooling air reduces the power generated by and efficiency of the gas turbine. In conventional cooling systems, the amount of cooling air has to be designed to match the gas temperature profile for the nozzle guide vane that is exposed to the hottest gas temperature, so that all guide vanes have the same acceptable lifetime. Summarizing, in conventional stator vane stages, in general a standard design of turbine vane arrangements is used, wherein the design of the vanes with respect to its heat resistance is a compromise to suit all circumferential temperature variations of the turbine.
GB 2 114 234 A discloses a combustion turbine with a single airfoil stator vane structure. A stator structure is provided including inner and outer shrouds with a hollow airfoil-shaped vane there between and with areas in the vicinity of the intersections of the shrouds with the airfoil vane walls being of reduced thickness relative to the remainder of the shrouds to provide improved properties of the material in these areas to better respond to thermal stresses imposed on the structure.
US 2007/0128020 A1 discloses a bladed stator for a Turbo-Engine. The bladed stator includes an inner platform and an outer platform and at least one blade fixed between said platforms. At least one of said platforms includes at least one flange having a first end fixed to the platform and a second, free end. The flange includes at least one non-opening free flexibility-increasing cut-out.